Cleaning process



' Patented June 9, 1936 PATENT OFFICE CLEANING PROCESS Paul McDorman,Dayton, Ohio, assignor, by

mesne assignments, to General Motors Corporation, a corporation ofDelaware 1 No Drawing. Application January 27, 1932,

' Serial No. 589,321

10 Claims. (01. 1488) This invention relates to a process for cleaningmetals. It is intended to be used for the cleaning of new metals,especially sheet steel for electro plating, dip plating, galvanizing,paint- 5 ing, vitreous and non-vitreous enameling, for the cleaning ofde-enameled sheets of metal, or for any other purpose in which steel mayrequire a clean surface.

Inthe manufacture of articles made of drawn metal, it is necessary touse a lubricant known as the drawing compound. This compound must beremoved from the drawn metal, otherwise the enamel, paint, plate orother finishing material usually applied to the article, will pull orbreak, thus causing a bare spot on the metal.

Heretofore it has been the custom to use as lubricants during thedrawing operation, drawing compounds made of soap, vegetable or otherwater soluble oils, because such compounds are the only compounds thatcould be successfully cleaned from the metal after it had beenfabricated. Such drawing compounds do not have good lubricatingproperties and for this reason the losses during the drawing operation,from tom metal, especially from deep drawn articles, have beenprohibitive andhave made the use of expensive specially made deepdrawing metals necessary for this type of work. I

My invention, which will be hereinafter specifically described, permitsthe use of hydrocarbon, mineral or petroleum oils, or compoundscontaining these materials as drawing compounds or lubricants. The useof this type of drawing compound, due to betterv lubricating properties,results in smaller drawing losses, larger variety of articles made,faster operation of the process, less scarring of the metals, lower costof the drawing compounds,'and, above all, will permit the use of muchcheaper metals. It will also- 40 permit the oiling of the metal at therolling mills to prevent subsequent rusting, :a very important itemwhere metal is to be maintained in storage for any length of time.

' Myv cleaning process consists essentially in treating the metal to becleaned with moist chlorine gas. Specifically, my process is carried outby passing the metal to be cleanedinto' an atmosphere of moist chlorinegas by allowing it to dip through a water seal, the water seal beingmaintained preferably at approximately 120 F.

The metal is maintained in the chlorine atmosphere for approximatelythree minutes, is then dipped or rinsed in water, and then returned tothe chlorineatmosphere for another three min- 65 utes. The metal isthenagain dipped or rinsed by passing through a water seal of substantiallyclearrunning water, and finally passed into a neutralizing solution.

The neutralizing solution may be any alkaline solution, such as sodaash, borax, silicates or com- 5 binations thereof. i

It is important in the above described process, that the chlorineatmosphere be maintained moist and that the metal treated should not beallowed to become dry either at the beginning of the op- 10 eration orwhile in the chlorine atmosphere. otherwise the products ofchlorinization become insoluble in water and can only be removed bymeans of acids. Also, chlorine gas acts very slowly or not at all on drymetal. 15

Preferably, as indicated above, the metal being treated should beintermittently treated with Y Water to remove theproducts ofchlorinization.

If this rinse is omitted, protective coatings may be formed on the metalwhich will greatly re- 20 tard the actionof the chlorine gas. Thewetting therefore has a two-fold function, and preferably the metalshould be wetted at least three times as set forth above.

I have found it advantageous to maintain the 25 flow of Water throughthe water baths as rapid as possible at all times and to maintain thewater baths slightly acid in character. Acid baths prevent the formationof hydroxides of iron which are insoluble in both alkaline or neutralsolutions. 30

By the foregoing outlined cleaning process, mineral, hydrocarbon, orpetroleum oil may be 'used as the drawing compounds, for such compoundsmay be easily removed by my cleaning process after the articles havebeen fabricated. 35

ferro antimoniate. This clings tenaciously to 40 the metal and cannot beremoved in the ordinary cleaning by acids or by mechanical means, and ifnot'removed will cause copper-heading and blistering of theground coatto follow. It is insoluble in water and all acids except nitric. 45 Whenthe piece is subjected to an acid bath, other than nitric, the hydrogenformed by the action of the acid on the metal reduces the sodium ferroantimoniate to antimony anhydride. This compound, although it isinsoluble in water and 50 acids and adheres to the metal, can be more orless successfully removed by vigorous hand scrubbing. By my process,treatmentin the chlorine bath will successfully remove the black smudgewithout the necessity of hand scrubbing.

My process may be carried out in any type of apparatus, but it isessential to use an apparatus that is made of material that will notreact with wet chlorine and that will prevent the escape of chlorine gasinto the atmosphere and that will permit the intermittent subjection ofthe metal to be treated first to the action of water, then to the actionof chlorine gas, etc.

While specific time intervals and temperatures have been indicatedthroughout the specification, it should be understood that these timeintervals and temperatures may be varied to suit the necessity of theparticular class of work being done. For example, in some cases, aslightly longer period of time in the chlorine atmosphere may benecessary.

What is claimed is as follows:

1. The method of cleaning metal comprising passing the metal through anatmosphere of moist chlorine gas at a temperature below the dissociationtemperature of HCl. I

2. The method of cleaning metal comprising passing the metal through anatmosphere of moist chlorine gas at a temperature below the dissociationtemperature of HCl and neutralizing the treated metal.

3. The process of cleaning metal which comprises wetting the metal withwater, reacting the moist metal with moist chlorine gas in an atmosphereof moist chlorine gas.

4. The process of cleaning metal which comprises wetting the metal withwater, reacting the moist metal with moist chlorine gas in an atmosphereof moist chlorine gas'and neutralizing the treated metal.

5. The process of cleaning metal comprising passing the metal to betreated through a water metal with moist chlorine gas, in an atmosphereof moist chlorine gas again wetting the, metal, and again interactingthe metal with moist chlorine gas.

8. The process of cleaning metal comprising wetting the metal withwater, interacting the metal with moist chlorine gas, again wetting themetal, again interacting the metal with moist chlorine gas in anatmosphere of moist chlorine gas, and finally neutralizing the treatedmetal.

9.-The process of cleaning metal which com prises interacting the metalwith chlorine gas in an atmosphere of moist chlorine gas whilemaintaining the metal moist and while excluding the air from contactwith the metal.

10. The process of cleaning metal which comprises passing the metal tobe treated through a water seal into a chamber containing moist chlorinegas, removing the treated metal from the chamber through a water sealand maintaining the water seal at approximately F.

PAUL MGDORMAN.

